Give the standard line notation for each cell in Exercises...

Key Concepts

Standard Line Notation

Standard line notation is a systematic method for representing the components and structure of an electrochemical cell in a concise diagram. It displays the arrangement of the electrodes and electrolyte solutions, using specific line symbols to depict interfaces and phase boundaries, which helps in clearly understanding the flow of electrons and the chemical reactions taking place at each electrode.

Electrochemical Cell Components

The key components of an electrochemical cell include the anode, where oxidation occurs, and the cathode, where reduction occurs, along with the electrolyte solutions that facilitate ion transfer. This notation helps to clearly illustrate which reactants and products are present on each side of the cell, thereby linking the physical setup to the chemical processes involved.

Phase Boundary Representation

Within standard line notation, phase boundaries are indicated by vertical lines that separate different phases or materials in the cell. A single vertical line is typically used to denote a transition between an electrode and its adjacent electrolyte, while a double vertical line represents the salt bridge or junction between two different electrolyte solutions. This representation is essential for tracking where changes in the chemical environment occur within the cell.

Transcript

00:01 In order to write the line notation for the electrochemical cells found in exercises 37 and 41, we first need to know the generic form of line notation.

00:14 The line notation always lists the components of the anode on the left hand side and the cathode on the right hand side.

00:22 Typically the components of the anode are represented as the solid electrode first, a single line to represent a phase transition, and then a list of the things that are found in solution.

00:36 We then have a double line to represent the salt bridge, and then we have the cathode compartment, which will be what's in solution first, and then a line to represent a phase transition from the solution to the electrode.

00:53 If there's no solid electrode that is found in the half reactions, then the electrode that is added is typically platinum.

01:05 For the first chemical reaction found in 37a, we have chromium 3 plus going to dichromate and chlorine gas going to chloride.

01:17 We see the chlorine is being reduced and the chromium is then being oxidized.

01:22 Whatever is oxidized is the anode and whatever is reduced is the cathode.

01:28 So we'll have our platinum with what is oxidized, the half cell containing the chromium and the dichromate.

01:37 It's not obvious in this chemical reaction, but if you balanced it appropriately as requested in problem 37a, you will have included water and hydrogen ions.

01:50 The hydrogen ions will become part of the oxidation or the anode half reaction.

01:57 We then have our double line to represent the salt bridge, and then we have what is being reduced, or the cathode compartment, the chloride, oftentimes, you'll see this chlorine written with a line separating it.

02:12 If we want to emphasize there's a phase transition, or other times we might just see and recognize that the chlorine gas has been dissolved in the aqueous solution, and we won't see the line.

02:27 We'll just see a comma.

02:36 And then last of all, many line notations will have, but it's not required, unless your instructor tells you so.

02:43 Concentrations.

02:46 So we'd have the concentration of chromium, concentration of dichromate, concentration of hydrogen ion, and so forth.

02:54 The concentration, typically written just after it, in parentheses.

03:01 For the next chemical reaction, we have copper 2 plus reacting with magnesium, going to magnesium 2 plus, and copper solid.

03:12 So we see that copper is being reduced from 2 plus to zero and magnesium is being oxidized.

03:20 So again, what is oxidized is the anode and that will be listed first...

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